This application is based on and incorporates herein by reference Japanese Patent Application No. 2002-103402 filed on Apr. 5, 2002.
1. Field of the Invention
The present invention relates to a high pressure fuel supply device of a pressure accumulating type.
2. Description of Related Art
A high pressure fuel supply device of a pressure accumulating type has been proposed as a high pressure fuel supply device of, for example, a diesel engine. In the high pressure fuel supply device, high pressure fuel is accumulated in a pressurized state in a pressure accumulation chamber formed in a pressure accumulator vessel and is supplied to each corresponding fuel injection device. Fuel passages are also formed in the pressure accumulator vessel. Each fuel passage is communicated with the accumulation chamber and conducts fuel to the accumulation chamber or conducts fuel from the accumulation chamber. An axis of the accumulation chamber is generally perpendicular to an axis of each fuel passage. Thus, an edged corner is formed in a connection between the accumulation chamber and the corresponding fuel passage.
Lately, to meet a demand for improving exhaust gas purification and also a demand for improving combustion efficiency, it is required to increase fuel injection pressure to further atomize fuel mist.
However, when the pressure of fuel accumulated in the accumulation chamber is increased, stress, which is applied from the pressure of fuel in the accumulation chamber to the accumulator vessel, is disadvantageously increased. In the case where the edged corner is formed in the connection between the accumulation chamber and the corresponding fuel passage, the stress applied to the accumulator vessel is concentrated in the edged corner.
In Japanese Unexamined Patent Publication No. 2000-73908, in order to address the above disadvantage, for example, there has been proposed a high pressure fuel supply device, which has a pressure accumulator vessel that includes an inner member and an outer member. In this high pressure fuel supply device, the inner member is press fitted into the outer member to apply compressive pre-stress to the inner member to reduce tensile stress applied from the fuel in the accumulation chamber to the inner member. However, in the high pressure fuel supply device disclosed in Japanese Unexamined Patent Publication No. 2000-73908, since the accumulator vessel includes the outer member and the inner member, the number of components is disadvantageously increased, and the total manufacturing time of the high pressure fuel supply device is also disadvantageously increased.
Furthermore, there has been proposed another technique for chamfering the edged corner in the connection between the accumulation chamber and the fuel passage through an electrolytic process to avoid concentration of stress in the corner. In this case, the chamfered section, which is chamfered through the electrolytic process, has a rough surface, which likely causes localized concentration of stress in the chamfered section. To address this disadvantage, the surface of the corner is smoothed through an abrasive flow machining process applied to the interior of the accumulator vessel after each corner is chamfered thorough the electrolytic process. However, the abrasive flow machining process disadvantageously requires a relatively long processing time. Furthermore, when the abrasive flow machining process is performed, particles, which are generated upon abrasion of the accumulator vessel, or abrasive material, which is contained in the abrasive fluid, may be left as residual debris in the processed accumulator vessel. Thus, a delicate washing process is required after the abrasive flow machining process. This disadvantageously results in an increase in the processing time.
Thus, it is an objective of the present invention to provide a high pressure fuel supply device, which minimizes concentration of stress in an accumulator vessel of the high pressure fuel supply device and improves pressure resistivity of the accumulator vessel to improve reliability of the high pressure fuel supply device without increasing the number of components of the high pressure fuel supply device and without leaving an substantial amount of residual debris in the high pressure fuel supply device.
It is another objective of the present invention to provide a manufacturing method of a high pressure fuel supply device, which allows a reduction in a total processing time of the high pressure fuel supply device without leaving a substantial amount of residual debris in the high pressure fuel supply device.
To achieve the objectives of the present invention, there is provided a high pressure fuel supply device having a pressure accumulator vessel that includes a pressure accumulation chamber, a fuel passage and a chamfered section. The pressure accumulation chamber extends in an axial direction of the pressure accumulator vessel. The fuel passage fluidly communicates between the accumulation chamber and an outside of the pressure accumulator vessel. The chamfered section is formed in a connection between the accumulation chamber and the fuel passage. An inner plated part, which includes a plating layer, is formed along a wall surface of the accumulation chamber, a wall surface of the fuel passage and a wall surface of the chamfered section.
To achieve the objectives of the present invention, there is also provided a manufacturing method of a high pressure fuel supply device, to which an external fuel pipe is joined. In the method, an axial hole, a branched hole and a chamfered section are first formed in a bar member. The axial hole extends in an axial direction of the bar member. The branched hole fluidly communicates between the axial hole and an outside of the bar member. The chamfered section is formed in a connection between the axial hole and the branched hole. Then, a connecting portion and a sealing portion are formed in the bar member. The connecting portion is formed to join with the external fuel pipe in such a manner that the fuel pipe is securely held by the connecting portion and is fluidly communicated with the branched hole. The sealing portion is formed adjacent to the connecting portion to fluid-tightly engage with the fuel pipe. Thereafter, a removable sealing member is installed in the bar member in such a manner that the sealing member engages the connecting portion and the sealing portion to fluid-tightly separate the axial hole and the branched hole from the connecting portion and the sealing portion. Then, a plated part, which includes a plating layer, is formed along a wall surface of the axial hole, a wall surface of the branched hole and a wall surface of the chamfered section.
To achieve the objectives of the present invention, there is further provided a manufacturing method of a high pressure fuel supply device, to which an external fuel pipe is joined. In the method, an axial hole, a branched hole and a chamfered section are formed in a bar member. The axial hole extends in an axial direction of the bar member. The branched hole fluidly communicates between the axial hole and an outside of the bar member. The chamfered section is formed in a connection between the axial hole and the branched hole. Then, a plated part, which includes a plating layer, is formed along a wall surface of the axial hole, a wall surface of the branched hole and a wall surface of the chamfered section. Thereafter, a connecting portion and a sealing portion are formed in the bar member that includes the inner plated part. The connecting portion is formed to join with the external fuel pipe in such a manner that the fuel pipe is securely held by the connecting portion and is fluidly communicated with the branched hole. The sealing portion is formed adjacent to the connecting portion to fluid-tightly engage with the fuel pipe.